Automatic or semi-automatic firearms typically include a bolt that cycles backward and forward between shots. The bolt acts to cycle a spent (or fresh) cartridge casing from the firing chamber of the firearm and to load a fresh cartridge for subsequent firing. Depending on the particular firearm, automated movement of the bolt may be propelled by recoil of the firearm and/or expanding gas associated with discharge of a previous round. Rearward movement of the bolt causes an extractor to engage and draw the spent (or fresh) casing from the firing chamber. The bolt returns forward, often under action of a spring, after the casing is ejected from the firearm. Forward movement of the bolt engages a fresh cartridge from a magazine and pushes the cartridge into the firing chamber for subsequent firing.
Automated cycling of a bolt may not occur under all circumstances. An operator may cycle a bolt manually to initially load a fresh cartridge into the firing chamber from a magazine that has just been loaded into the firearm. Similarly, a bolt may not fully cycle after the final cartridge from a magazine is spent. There may be additional instances when an operator wishes to cycle the action of a firearm (i.e., move the bolt through a cycle), such as for inspection or to clear a cartridge.
A charging handle is incorporated into some firearms, including AR-10, AR-15, M16, and M4 type firearms, that may be pulled by an operator to move a bolt and any associated components rearward through a portion of the action of the firearm. Conventional charging handles includes a finger that extends downward within the firearm to engage the bolt carrier when the charging handle is actuated by an operator. This finger, among other features, prevents the charging handle from being assembled to the firearm in more than one configuration.